Self-harm is so addictive. I have always thought the urges were like getting your wheels stuck in mud, the more time you spent spinning them, the more stuck you get.
I really hope you go back to school and allow the school counselor to talk to you. More than likely they will asses the self-harm, any suicidal thoughts, ask you what's been going on to cause this and then contact your parents. Most school counselors don't have master's degrees but hopefully you'll be sent to a school social worker or school psychologist (they do have more than a bachelor's).